We prepared poly(vinylidene fluoride) (PVDF)/multiwalled carbon nanotube (MWCNT) nanocomposites using the electrospinning process and investigated the effects of varying the MWCNT content, as well as the additional use of drawing and poling on the polymorphic behavior and electroactive (piezoelectric) properties of the membranes obtained. Fourier transform infrared spectroscopy and wide-angle X-ray diffraction revealed that dramatic changes occurred in the β-phase crystal formation with the MWCNT loading. This was attributed to the nucleation effects of the MWCNTs as well as the intense stretching of the PVDF jets in the electrospinning process. The remanent polarization and piezoelectric response increased with the amount of MWCNTs and piezoelectric β-phase crystals. A further mechanical stretching and electric poling process induced not only highly oriented β-phase crystallites, but also very good ferroelectric and piezoelectric performances. In the drawn samples, the interfacial interaction between the functional groups on the MWCNTs and the CF 2 dipole of PVDF chains produced a large amount of βphase content. In the poled samples, the incorporation of the MWCNTs made it easy to obtain efficient charge accumulation in the PVDF matrix, resulting in the conversion of the α-phase into the β-phase as well as the enhancement of remanent polarization and mechanical displacement.

Pelvic reconstruction after sacral resection is challenging in terms of anatomical complexity, excessive loadbearing, and wide defects. Nevertheless, the technological development of 3D-printed implants enables us to overcome these difficulties. Here, we present a case of sacral osteosarcoma surgically treated with hemisacrectomy and sacral reconstruction using a 3D-printed implant. The implant was printed as a customized titanium prosthesis from a 3D real-sized reconstruction of a patient's CT images. It consisted mostly of a porous mesh and incorporated a dense strut. After 3-months of neoadjuvant chemotherapy, the patient underwent hemisacretomy with preservation of contralateral sacral nerves. The implant was anatomically installed on the defect and fixed with a screw-rod system up to the level of L3. Postoperative pain was significantly low and the patient recovered sufficiently to walk as early as 2 weeks postoperatively. The patient showed left-side foot drop only, without loss of sphincter function. In 1-year follow-up CT, excellent bony fusion was noticed. To our knowledge, this is the first report of a case of hemisacral reconstruction using a custom-made 3D-printed implant. We believe that this technique can be applied to spinal reconstructions after a partial or complete spondylectomy in a wide variety of spinal diseases.

A thermoelectric nanocomposite material was prepared using the bismuth–antimony–telluride alloy (Bi0.5Sb1.5Te3 (BST)) nanorod-forming process in poly­(3,4-ethylenedioxythiphene):polystyrene (PEDOT:PSS) solution. A new two-step reduction process allows easy formation of the BST-alloy in nanorods as well as the simultaneous oxidation of PEDOT:PSS. Scattering at the interface between BST nanorods and the PEDOT:PSS facilitates even lower thermal conductivity, whereas high electron conductivity in BST nanorods and PEDOT:PSS could significantly improve the thermoelectric performance of the nanocomposite. The BST-PEDOT:PSS nanocomposite has a Seebeck coefficient of 49 μV K–1 and an electrical conductivity 1285 S cm–1 at room temperature. The corresponding power factor is 308 μW m–1 K–2 to yield a figure of merit (ZT) = 0.484 at room temperature recording the highest ZT value among the organic–inorganic thermoelectric materials, which proves that this nanocomposite material is close to fulfilling the requirement for efficient waste energy harvesting at low temperatures. The nanocomposite materials are readily synthesized, environmentally friendly, air-stable, and solution-processable to easily produce patterns on large areas. The easy preparation process provides a viable technology platform for the fabrication of highly efficient thermoelectric nanocomposites for waste energy harvesting at low temperature.

No abstract

Aqueous potassium salt solutions of l-alanine and l-proline were investigated as carbon dioxide (CO2) absorbents. The CO2 absorption capacities and absorption heats (−ΔH abs) of the aqueous amino acid salts were measured in a semi-batch absorption system and differential reaction calorimeter (DRC). The solution experiments tested concentrations of 2.5 M and were carried out at 298 and 313 K. The 13C and 1H nuclear magnetic resonance (NMR) spectra were used to identify the species distributions in the CO2-loaded absorbents. The absorption properties were compared to those of the commercial monoethanolamine (MEA) absorbent, revealing that the CO2 loading capacity was higher than that of MEA (0.68 mol of CO2/mol of solute for the potassium salt of l-alanine > 0.5 mol of CO2/mol of solute for MEA). The absorption heat was lower than that of MEA at 298 K (53.26 kJ/mol of CO2 for the potassium salt of l-alanine < 81.77 kJ/mol of CO2 for MEA).

A series of polyimide (PI) nanocomposite films with different loadings of aminophenyl functionalized graphene nanosheets (AP-rGO) was fabricated by in situ polymerization. AP-rGO, a multifunctional carbon nanofiller that can induce covalent bonding between graphene nanosheets and the PI matrix, was obtained through the combination of chemical reduction and surface modification. In addition, phenyl functionalized graphene nanosheets (PrGO) were prepared by phenylhydrazine for reference nanocomposite films. Because of homogeneous dispersion of AP-rGO and the strong interfacial interaction between AP-rGO and the PI matrix, the resulting nanocomposite films that contained AP-rGO exhibited reinforcement effects of mechanical properties and oxygen barrier properties that were even better than those of pure PI and the reference nanocomposite films. In comparison to the tensile strength and tensile modules of pure PI, the composite films that contained AP-rGO with 3 wt % loading were increased by about 106% (262 MPa) and 52% (9.4 GPa), respectively. Furthermore, the oxygen permeabilities of the composites with 5 wt % filler content were significantly decreased, i.e., they were more than 99% less than the oxygen permeability of pure PI.

In this article, we detail an effective way to improve electrical, thermal, and gas barrier properties using a simple processing method for polymer composites. Graphene oxide (GO) prepared with graphite using a modified Hummers method was used as a nanofiller for r‐GO/PI composites by in situ polymerization. PI composites with different loadings of GO were prepared by the thermal imidization of polyamic acid (PAA)/GO. This method greatly improved the electrical properties of the r‐GO/PI composites compared with pure PI due to the electrical percolation networks of reduced graphene oxide within the films. The conductivity of r‐GO/PI composites (30:70 w/w) equaled 1.1 × 101 S m−1, roughly 1014 times that of pure PI and the oxygen transmission rate (OTR, 30:70 w/w) was reduced by about 93%. The Young's modulus of the r‐GO/PI composite film containing 30 wt % GO increased to 4.2 GPa, which was an approximate improvement of 282% compared with pure PI film. The corresponding strength and the elongation at break decreased to 70.0 MPa and 2.2%, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40177.

No abstract